CN116640903A - A LF furnace desulfurization method for slab continuous casting ultra-low sulfur steel - Google Patents

Abstract

The invention discloses a desulfurizing method of a slab continuous casting ultralow-sulfur steel LF furnace, which comprises the steps of obtaining molten steel parameters entering the LF furnace; according to the parameters, adding refining slag into the molten steel to carry out desulfurization treatment; wherein the parameters include mass, composition and approach temperature, and the desulfurization treatment controls the sulfur content in the desulfurized molten steel to be 0.001-0.0030wt.%. In the process of refining the ultralow-sulfur steel in the LF furnace, the slag quantity is properly controlled, the moderate oxygen activity in the molten steel is controlled, and the process of adding aluminum-containing slag and aluminum particles is adopted, so that the effective control of the sulfur content can be ensured, the capability of continuous casting can be met, the LF desulfurization cost is reduced, the operation is simple and easy to control in the smelting and refining operation site, the sulfur content can be stably controlled, the quality of continuous casting products is ensured, and the method has higher economic benefit.

Description

A LF furnace desulfurization method for slab continuous casting ultra-low sulfur steel

technical field

The invention relates to the technical field of iron and steel metallurgy, in particular to a LF furnace desulfurization method for slab continuous casting ultra-low sulfur steel.

Background technique

Sulfur is a harmful impurity element in steel materials (except for a very small number of steel types used to improve cutting performance, such as gear steel). The level of sulfur content is the main feature of steel quality. Quality level, the pursuit of ultra-low sulfur is the general consensus of the steel industry.

The excellent quality represented by ultra-low sulfur in plate ultra-low sulfur steel is the main indicator of the production capacity level in steel mills. The general composition design feature of this type of steel is low carbon, low silicon, high manganese aluminum killed steel, the composition of the steel is low in carbon, extremely low in sulfur, high in aluminum and high in manganese, and also contains niobium, vanadium, titanium, chromium One or more beneficial elemental substances added for performance adjustment such as , copper, etc. The composition is complex and difficult to control. The most difficult thing is to control sulfur to the ideal material level. The general basic composition range is [carbon]: 0.05%-0.20 %, [Sulphur]: 0.0002%-0.0050%, [Manganese] 0.35%-1.65%. This type of steel has the reputation of super high-quality steel due to its extremely low sulfur content, and it is extremely difficult to produce.

When this type of steel comes from the difference in the molten steel conditions of the primary furnace, the sulfur content of the steel from LF is higher (for example, sulfur ≥ 0.0050%, and LF is required for desulfurization operations, which must meet the basic conditions of sulfur < 0.005%. In addition, refining desulfurization needs Increase LF consumption (auxiliary materials, deoxidizer alloys, power consumption, etc.), and meet the various requirements of time and cost reduction under the premise of ensuring successful desulfurization, which brings great difficulty to the secondary refining of slab ultra-low sulfur steel molten steel. However, continuous casting requires molten steel refining to process qualified molten steel within a given time. How to adopt effective technologies in molten steel smelting and refining links to improve the refining rate of this type of steel and ensure the sulfur content requirements of continuous casting molten steel is a key issue in iron and steel metallurgy. important issues in the field for a long time.

For the process flow of the steel plant: desulfurization-converter-LF-slab continuous casting, the desulfurization process of the steel plant can achieve the desulfurization of molten iron to a very low level, but after the operation of the converter process and other operations, the sulfur content of the refined LF steel is 0.0050 %—0.0100%, while the ultra-low sulfur steel needs to fluctuate between 0.001% and 0.005% after refining, and it will either be deeply desulfurized or cannot be desulfurized, causing large fluctuations in slab continuous casting production, and the slag used for desulfurization Therefore, it is necessary to explore the desulfurization process of slab ultra-low sulfur steel, provide a set of desulfurization strategies that can be implemented on site, and find a solution to the thorny problem of ultra-low sulfur steel desulfurization. The method is of great significance to the stable and smooth production of slab ultra-low sulfur steel continuous casting.

Contents of the invention

In order to solve the problems existing in the prior art, the present invention provides a LF furnace desulfurization method for slab continuous casting ultra-low sulfur steel, comprising:

Obtain the parameters of molten steel entering the LF furnace;

Add refining slag to the molten steel for desulfurization according to the parameters;

Wherein, the parameters include quality, composition and entry temperature, and the desulfurization treatment controls the sulfur content in the desulfurized molten steel to 0.001-0.0030wt.%.

Optionally, said acquisition of molten steel parameters entering the LF furnace includes,

After the molten steel enters the LF furnace, the weight of the molten steel and the temperature at the station are measured; then the molten steel is blown with argon to measure the composition of the molten steel.

Optionally, according to the parameters, adding refining slag to molten steel for desulfurization treatment includes,

Add aluminum particles and slag adjusting agent according to the sulfur content of molten steel, and carry out desulfurization treatment under step-by-step heating;

The slagging agent includes Al-Al ₂ O ₃ slag material, lime and fluorite.

Optionally, according to the sulfur content of molten steel, 0.2-0.8kg of aluminum particles, 1.5-3.0kg of Al-Al ₂ O ₃ slag, 5.0-10.0kg of lime and 1.2-3.0kg of fluorite.

Optionally, the sulfur content of the molten steel is 0.0050-0.0100wt.%.

Optionally, the composition of the Al-Al ₂ O ₃ slag is calculated by mass percentage, the Al content is ≥ 20 wt.%, and the Al ₂ O ₃ content is ≥ 15 wt.%.

Optionally, the content of CaO in the lime>80wt.%;

The content of CaF ₂ in the fluorite is >80wt.%.

Optionally, the stepwise heating includes,

According to the entering temperature of molten steel and the quality of refining slag, add the first refining slag for the first step of heating;

After the first step of heating, check the slagging condition, blow the heated molten steel with argon and stir to measure its composition, add the second refining slag for the second step of heating.

Optionally, the mass of the first refining slag accounts for 60-90wt.% of the mass of the refining slag.

Optionally, adding the first refining slag to carry out the first step of heating adopts batch feeding, and each batch is 200-500kg.

Compared with the prior art, the present invention has the following beneficial effects:

During the refining process of ultra-low sulfur steel in LF furnace, the invention properly controls the amount of slag, controls the moderate oxygen activity in molten steel, adopts the process of adding aluminum-containing slag material and adding aluminum particles, which can ensure effective control of sulfur content and meet the requirements of continuous production. Casting ability, reduce LF desulfurization cost, simple operation and easy control at the smelting and refining operation site, can stably control the sulfur content, ensure the quality of continuous casting products, and have high economic benefits.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention can be realized and obtained by the steps pointed out in the specification.

Detailed ways

Neither the endpoints of the ranges nor any values disclosed herein are limited to such precise ranges or values, and these ranges or values are understood to include values approaching these ranges or values. For numerical ranges, between the endpoints of each range, between the endpoints of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, these values Ranges should be considered as specifically disclosed in the present invention.

The inventive idea of the present invention is: during the refining process of ultra-low sulfur steel in LF furnace, properly control the amount of slag, control the moderate oxygen activity in molten steel, adopt the process of adding aluminum-containing slag material and aluminum particles, and effectively control the sulfur content.

LF furnace (LADLE FURNACE) is the ladle refining furnace, which is the main refining equipment outside the furnace in steel production. LF furnace generally refers to the refining furnace in the steel industry, which is a special form of electric arc furnace. LF furnace is often used for desulfurization, temperature regulation of molten steel, fine-tuning of precise composition of molten steel, improvement of purity of molten steel and slagging operation.

For this reason, the present invention provides a kind of slab continuous casting ultra-low sulfur steel LF furnace desulfurization method, comprising:

Obtain the parameters of molten steel entering the LF furnace;

Add refining slag to the molten steel for desulfurization according to the parameters;

Wherein, the parameters include quality, composition and entry temperature, and the desulfurization treatment controls the sulfur content in the desulfurized molten steel to 0.001-0.0030wt.%.

In an optional embodiment of the present invention, the molten steel entering the LF furnace is molten steel smelted in the primary smelting furnace, and the steel is tapped from the primary smelting furnace for deoxidation alloying with aluminum-iron (wire), and at the same time, ferromanganese is added for initial alloying.

In an optional embodiment of the present invention, said obtaining the parameters of the molten steel entering the LF furnace includes measuring the weight and temperature of the molten steel after the molten steel enters the LF furnace; then performing argon blowing on the molten steel to measure the composition of the molten steel.

Preferably, the molten steel is blown with argon for 3-5 minutes after entering the LF furnace, and samples are taken to test the composition of the molten steel (excluding oxygen).

In an optional embodiment of the present invention, according to the parameters, adding refining slag to molten steel for desulfurization treatment includes:

Add aluminum particles and slag adjusting agent according to the sulfur content of molten steel, and carry out desulfurization treatment under step-by-step heating;

The slagging agent includes Al-Al ₂ O ₃ slag material, lime and fluorite. Lime is a low-value slag material containing CaO, and fluorite is a low-value slag material containing _CaF2 .

Preferably, according to the sulfur content of molten steel, 0.2-0.8kg of aluminum particles, 1.5-3.0kg of Al-Al ₂ O ₃ slag, 5.0-10.0kg of lime and 1.2-3.0kg of fluorescein are added to each ton of molten steel. stone. It should be noted that aluminum particles are used to reduce the oxidation of slag. If aluminum is an alloying element for producing slabs, the actual addition of aluminum particles needs to be adjusted according to the actual content of alloying elements.

Preferably, the sulfur content of the molten steel is 0.0050-0.0100wt.%.

Preferably, the composition of the Al-Al ₂ O ₃ slag is calculated by mass percentage, the content of Al ≥ 20 wt.%, and the content of Al ₂ O ₃ ≥ 15 wt.%.

Preferably, the CaO content in the lime is >80wt.%; the CaF ₂ content in the fluorite is >80wt.%.

The operation of heating slag is basically divided into two steps of desulfurization heating method. The determination of the first heating time depends on the temperature of molten steel entering the station and the amount of slag added during the period; because the amount of slag added is seriously related to the amount of slag and component content in the primary furnace and The original element content in molten steel such as the sulfur content of the incoming steel.

In an optional embodiment of the present invention, the step-by-step heating includes, according to the incoming temperature of molten steel and the quality of the refining slag, adding the first refining slag for the first step of heating; after the first step of heating, check the For slag, the heated molten steel is blown with argon and stirred to measure its composition, and the second refining slag is added for the second step of heating.

Preferably, after the first step of heating is completed, switch to a large flow of argon to stir, and take a sample after 8 minutes to test the composition of the molten steel; continue blowing argon and stir while waiting for the composition to be tested.

Preferably, the mass of the first refining slag accounts for 60-90wt.% of the mass of the refining slag.

Preferably, adding the first refining slag to carry out the first step of heating adopts batch feeding, each batch is 200-500kg.

With reference to the condition that the sulfur content of molten steel entering the LF furnace is 0.005wt.% to 0.010wt.%, various materials are added to provide a desulfurization reference feeding table for slab ultra-low sulfur steel (target sulfur 0.0010wt.%), see Table 1 below , can interpolate to read the type and quantity of added materials.

Table 1 Desulfurization Reference Addition Table

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention. In the examples, each original reagent material can be obtained commercially, and the experimental methods without specific conditions are conventional methods and conventional conditions well known in the art, or according to the conditions suggested by the instrument manufacturer.

Example 1

A LF furnace desulfurization method for slab continuous casting ultra-low sulfur steel, for the treatment of steel grade Q345B, the basic requirements of steel grade composition: 0.14wt.%-0.20wt.%C, 0.30wt.%-0.50wt.%Mn, S ≤0.003wt.%, 0.030-0.055wt.%Ti, 0.015-0.05wt.%Als, 0.15wt.%-0.35wt.%Si, including the following steps,

Step 1. Molten steel LF enters the station operation: after the molten steel enters the LF furnace, the measured molten steel weight is 132.6 tons and the incoming temperature is 1589°C; then the molten steel is blown with argon for 3 minutes, and the measured composition of the molten steel is 0.15wt.%C , 0.42wt.% Mn, 0.19wt.% Si, 0.036wt.% Als, 0.0067wt.% S;

Step 2, LF slagging: Add Al-Al ₂ O ₃ slag material (Al content ≥ 20wt.%, Al ₂ O ₃ content ≥ 15wt.%) 282Kg, lime (CaO content > 80wt.%) to molten steel wt.%) 945Kg, aluminum particles 72Kg, fluorite (CaF ₂ content > 80wt.%) 260Kg, add ferro-titanium (titanium content 40wt.%) 231Kg, LF electric heating time 21 minutes (first LF electric heating 13 minutes , the second heating for 8 minutes), the temperature measurement was 1589°C, and the outbound sampling test components were 0.16wt.%C, 0.43wt.%Mn, 0.21wt.%Si, 0.046wt.%Als, 0.0012wt.%S, 0.052wt.%Ti, continuous casting sampling test composition 0.16wt.%C, 0.44wt.%Mn, 0.22wt.%Si, 0.039wt.%Als, 0.0008wt.%S, 0.044wt.%Ti.

Example 2

A LF furnace desulfurization method for slab continuous casting ultra-low sulfur steel, for the treatment of steel grade Q345B, the basic requirements of steel grade composition: 0.14wt.%-0.20wt.%C, 0.30wt.%-0.50wt.%Mn, S ≤0.003wt.%, 0.030-0.055wt.%Ti, 0.015-0.05wt.%Als, 0.15wt.%-0.35wt.%Si, including the following steps,

Step 1. Molten steel LF enters the station operation: after the molten steel enters the LF furnace, the measured molten steel weight is 130.9 tons and the incoming temperature is 1582°C; then the molten steel is blown with argon for 3 minutes, and the measured composition of the molten steel is 0.15wt.%C , 0.42wt.% Mn, 0.19wt.% Si, 0.036wt.% Als, 0.0067wt.% S;

Step 2, LF slagging: Add Al-Al ₂ O ₃ slag material (Al content ≥ 20wt.%, Al ₂ O ₃ content ≥ 15wt.%) 292Kg, lime (CaO content > 80wt.%) to molten steel %) 987Kg, aluminum particles 77Kg, fluorite (CaF ₂ content > 80wt.%) 271Kg, add 222Kg of ferrotitanium (titanium content 40wt.%), LF electric heating time 23 minutes (first LF electric heating 14 minutes, second Secondary heating for 9 minutes), the temperature measurement was 1586°C, and the outbound sampling test components were 0.17wt.%C, 0.41wt.%Mn, 0.24wt.%Si, 0.045wt.%Als, 0.0014wt.%S, 0.049wt .%Ti, continuous casting sampling test composition 0.17wt.%C, 0.42wt.%Mn, 0.24wt.%Si, 0.036wt.%Als, 0.0011wt.%S, 0.042wt.%Ti.

In summary, in the process of refining ultra-low sulfur steel in LF furnace, the present invention properly controls the amount of slag, controls the moderate oxygen activity in molten steel, adopts the process of adding aluminum-containing slag and adding aluminum particles, which can ensure effective control of sulfur The sulfur content can meet the capacity of continuous casting, reduce the cost of LF desulfurization, the operation is simple and easy to control in the smelting and refining operation site, and the sulfur content can be stably controlled to ensure the quality of continuous casting products, which has high economic benefits.

Finally, it should be noted that: the above is only a preferred embodiment of the present invention, and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, it still It is possible to modify the technical solutions recorded in the foregoing embodiments, or to perform equivalent replacements on some of the technical features. Any modifications, equivalent replacements, improvements, etc. within the spirit and principles of the present invention shall be included in the within the protection scope of the present invention.

Claims (10)

1. The desulfurizing method for the slab continuous casting ultralow-sulfur steel LF furnace is characterized by comprising the steps of,

acquiring molten steel parameters entering an LF furnace;

according to the parameters, adding refining slag into the molten steel to carry out desulfurization treatment;

wherein the parameters include mass, composition and approach temperature, and the desulfurization treatment controls the sulfur content in the desulfurized molten steel to be 0.001-0.0030wt.%.

2. The method of claim 1, wherein the obtaining parameters of molten steel entering the LF furnace comprises,

measuring the weight of molten steel and the entering temperature after the molten steel enters an LF furnace; and then argon blowing treatment is carried out on the molten steel, and the components of the molten steel are measured.

3. The method of claim 1, wherein adding refining slag to molten steel for desulfurization treatment according to the parameters comprises,

adding aluminum particles and slag modifier according to the sulfur content of molten steel, and desulfurizing under step-by-step heating;

the slag modifier comprises Al-Al ₂ O ₃ Slag, lime and fluorite.

4. A method according to claim 3, wherein 0.2-0.8kg of aluminum particles and 1.5-3.0kg of Al-Al are added to each ton of molten steel according to the sulfur content of the molten steel ₂ O ₃ Slag, 5.0-10.0kg lime and 1.2-3.0kg fluorite.

5. The method of claim 4, wherein the sulfur content of the molten steel is 0.0050 to 0.0100wt.%.

6. The method of any one of claims 3-5, wherein the Al-Al ₂ O ₃ The slag comprises the components in percentage by mass that the content of Al is more than or equal to 20wt percent, and Al is added in the slag ₂ O ₃ The content of (2) is not less than 15wt.%.

7. The method according to claim 6, characterized in that the CaO content in the lime is >80wt.%;

CaF in the fluorite ₂ Content of (3)>80wt.％。

8. The method of claim 3, wherein the step heating comprises,

adding first refining slag according to the entering temperature of molten steel and the quality of the refining slag to perform first-step heating;

after the first step of heating, checking the slag melting condition, blowing argon into the heated molten steel, stirring to determine the components of the molten steel, and adding second refining slag for the second step of heating.

9. The method of claim 8, wherein the first refining slag mass comprises 60-90wt.% of the mass of the refining slag.

10. The method of claim 9, wherein the adding the first refining slag for the first heating step is performed using fed-batch 200-500kg per batch.